Link adaptation based on neighboring cell transmission information

ABSTRACT

The present disclosure provides a fine-grained link adaptation mechanism that allows for link adaptation at a resource block granularity. To this end, the fine-grained link adaptation mechanism can determine the effective signal-to-interference-plus-noise ratio for individual user equipment in a particular cell at the resource block granularity. This way, the transmitter can use the effective signal-to-interference-plus-noise ratio to adapt the modulation and coding scheme at the resource block granularity. The fine-grained link adaptation mechanism can be introduced to a long term evolution (LTE) network without substantial redesign of the LTE network.

FIELD OF THE DISCLOSURE

This disclosure relates generally to apparatus, systems, and methods forproviding a fine-grained link adaptation mechanism.

BACKGROUND

Wireless networks are telecommunication networks that use radio waves tocarry information from one node in the network to one or more receivingnodes in the network. Cellular telephony is characterized by the use ofradio cells that provide radio coverage for a geographic area, withmultiple cells arranged to provide contiguous radio coverage over alarger area. Wired communication can also be used in portions of awireless network, such as between cells or access points. Wirelesscommunication technologies are used in connection with many userequipment, including, for example, satellite communications systems,portable digital assistants (PDAs), laptop computers, and mobile devices(e.g., cellular telephones). Such devices can connect to a network(e.g., the Internet) as long as the user is within range of such awireless communication technology. Such devices can use connections tothe wireless networks to download video data.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a communication network that implements afine-grained link adaptation mechanism in accordance with someembodiments.

FIG. 2 illustrates a communication network that implements afine-grained link adaptation mechanism in accordance with universalmobile telecommunications systems (UMTS) network devices in accordancewith some embodiments.

FIG. 3 illustrates a base station in accordance with some embodiments.

FIG. 4 illustrates a process for determining an effective SINR for aparticular resource block in accordance with some embodiments.

DESCRIPTION OF EXAMPLE EMBODIMENTS Overview

Some embodiments include a method for communicating with a receiverusing a modulation and coding scheme (MCS). The method includesdetermining, at a transmitter in communication with the receiver in acommunications network, an interference adjustment factor that accountsfor a signal interference level for a particular resource block;determining the MCS for the receiver for the particular resource blockbased, at least in part, on the interference adjustment factor; andcommunicating with the receiver using the determined MCS.

Some embodiments include a network device. The network device includesone or more interfaces configured to provide wireless communication witha receiver; and a processor, in communication with the one or moreinterfaces, and configured to run a module stored in memory. The networkdevice is configured to determine an interference adjustment factor thataccounts for a signal interference level unique for a particularresource block; determine a modulation and coding scheme (MCS) for thereceiver for the particular resource block based, at least in part, onthe interference adjustment factor; and communicate with the receiverusing the determined MCS.

Some embodiments include a method for determining a modulation andcoding scheme (MCS) for a receiver. The method includes determining, ata transmitter in communication with the receiver, asignal-to-interference-plus-noise ratio (SINR) based on channel stateinformation received from the receiver; determining an adaptation factorbased on a predetermined limit of a number of packet retransmissions tothe receiver; determining an interference adjustment factor thataccounts for a signal interference level at a resource blockgranularity; and determining the MCS for the receiver at the resourceblock granularity based, at least in part, on the SINR, the adaptationfactor, and the interference adjustment factor.

Example Embodiments

Link adaptation relates to an ability to adapt the modulation, codingand other signal and protocol parameters to the conditions of the radiolink. For example, when the radio link condition is good, a transmittercan transmit data using a small amount of error correction, which allowsfor a high data transmission rate. On the other hand, when the radiolink condition is poor, a transmitter needs to transmit data using alarge amount of error correction and a more robust modulation scheme,which can limit the data transmission rate.

Transmitters can adapt a modulation and coding scheme (MCS) to a radiolink condition based, at least in part, on Level 1 (L1) controlinformation of the radio link. The L1 control information can includeone or more of a set of resource blocks (RBs) allotted to a receiver,transmission power (e.g., power spectral density) to the receiver,transmission history associated with the receiver (e.g., the history ofMCS, RBs assigned, ACK/NACK for past transmissions to the receiver),and/or a predetermined block error rate (BLER) on a given number ofhybrid automatic repeat request (H-ARQ) retransmissions to the receiver.

The L1 control information can also include channel state information.In some cases, transmitters can acquire the channel state informationfrom the receiver, which can measure the channel state information. Forexample, in Long Term Evolution (LTE) networks, a transmitter cantransmit a reference signal to a receiver, and the receiver can estimatea ratio of signal and noise, such as a Signal to Interference and NoiseRatio (SINR), of the channel based on the SINR of the reference signal.Subsequently, the receiver can use the estimated SINR of the channel todetermine a Channel Quality Indicator (CQI), and send the CQI to back tothe transmitter.

One of the factors that affects the radio link condition isinterference. In an LTE network, due to the orthogonal nature oforthogonal frequency-division multiple access (OFDMA) signals, there isno interference between signals within a cell. However, as signalsoriginating from different cells are not orthogonal in nature, a celledge user may experience interference due to signals from adjacentcells. LTE uses a frequency reuse of one, which indicates that adjacentcells can transmit signals on the same frequency band, resulting ininter-cell interference.

To a certain degree, traditional transmitters adapt the MCS to theinterference of signals from adjacent cells. For example, the CQI canaccount for an average interference level over a sub-band of frequencies(in case of the sub-band CQI) or over an entire cell bandwidth (in caseof the wideband CQI). However, traditional transmitters do not adapt theMCS to the interference of signals from adjacent cells at a RBgranularity. For example, if the signal transmission power levels in RBsare individually controlled, then the CQI would not provide an accuraterepresentation of the SINR on a given RB and the CQI cannot providesufficient information for a base station to adapt the signaltransmission at the RB granularity.

One may attempt to capture the interference information by usingreference signals having the same power (e.g., power spectral density)as the data signals and re-estimating the SINR of the channel every timethe data signals change their power profile. However, this scheme cannotbe implemented in the current release of LTE. Furthermore, this schemerequires the following steps every time the inter-cell interferencechanges: reference signal transmission by the transmitter to a receiver(e.g., user equipment (UE)), reference signal detection by the receiver,and CQI feedback by the receiver to the transmitter. Incorporating theseadditional steps in LTE can involve a significant re-design of thenetwork, and can entail significant control overhead.

The disclosed embodiments provide a fine-grained link adaptationmechanism that allows for link adaptation at the RB granularity. To thisend, the fine-grained link adaptation mechanism can determine theeffective SINR for an individual receiver, such as UE, in a particularcell at the RB granularity, and thus the transmitter can use theeffective SINR to adapt the MCS at the RB granularity. The fine-grainedlink adaptation mechanism can be introduced to an LTE network withoutsubstantial redesign of the LTE network.

In some embodiments, under the fine-grained link adaptation mechanism, atransmitter can determine an effective SINR for a particular receiver(e.g., UE) in a particular cell based on at least three factors: (1) aSINR derived from channel state information (e.g., CQI), (2) anadaptation factor selected based on (a) the predetermined limit on thenumber of packet retransmissions for successful communication and/or (b)the MCS previously assigned to the particular receiver and theparticular cell, and (3) an interference adjustment factor that accountsfor the inter-cell interference at the RB granularity. While traditionaltransmitters have used the SINR from the CQI and/or the adaptationfactor for determining the effective SINR, traditional transmittersfailed to use the interference adjustment factor to account for theinter-cell interference at the RB granularity.

In some embodiments, the interference adjustment factor for a particularRB can be determined based on a difference between (1) the SINR derivedfrom channel state information, such as a CQI, for a sub-band offrequencies including the particular RB, and (2) the SINR of thedownlink data channel, such as the Physical Downlink Shared Channel(PDSCH), for the particular RB. This way, the interference adjustmentfactor can explicitly account for the difference in SINR for each RB.

In some embodiments, the difference between (1) the SINR derived fromthe channel state information, and (2) the SINR of the downlink datachannel can be determined based on a ratio of (a) the signaltransmission power on the downlink data channel, and (b) thetransmission power of the cell specific reference signal (CRS) for boththe serving cell and neighboring cells. Since the transmitter is withinthe serving cell, the transmitter can easily obtain the signaltransmission power on the downlink data channel and the transmissionpower of the reference signal for the serving cell. In some cases, thetransmitter can obtain the signal transmission power on the downlinkdata channel and the transmission power of the reference signal forneighboring cells based on resource block scheduling information, whichmay be received by the transmitter as a part of a Relative NarrowbandTransmit Power (RNTP) message.

FIG. 1 illustrates a communication network that implements afine-grained link adaptation mechanism in accordance with someembodiments. FIG. 1 includes a number of transmitters, such as basestations, that may implement the fine-grained link adaptation mechanism.The base stations can include a 1×RTT transceiver 100, a high-ratepacket data (HRPD) transceiver 102, and an evolved high-rate packet data(eHRPD) transceiver 104, each of which can connect to an access network106. The base stations can also include an evolved Node B (eNodeB)transceiver 108, which is an LTE network radio network component thatconnects to an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN)110. Other base stations such as Wi-Fi, Femto, WiMAX, or any other radiospectrum technology, can use a transceiver shown generally as 112 toconnect user equipment (UE) 134 to the network using a broadband orother access network.

The access network 106 can communicate with an access gateway 116 thatimplements a combination of functionalities such as a packet dataserving node (PDSN), a HRPD serving gateway (HSGW), and a servinggateway (SGW). In operation, the PDSN functionality can be used with1×RTT 100, the HSGW functionality can be used with HRPD 102 and eHRPD104, and the SGW functionality can be used with the eNodeB 108. Theaccess gateway 116 can communicate with an anchor gateway 118, which canimplement a packet data network gateway (PGW) and a Home Agent (HA), anda mobility management entity (MME) 120. On the access network side, theanchor gateway 118 can also communicate with an evolved packet datagateway (ePDG) 122 that provides connectivity to the Wi-Fi/Femto/othertransceiver 112. On the packet core side, the anchor gateway cancommunicate with the operator's IP service domain 124, the internet 126,IP multimedia subsystem (IMS) 128, a data center 132, and a video server136. An authentication, authorization, and accounting (AAA) server/homesubscriber server (HSS) 130 can communicate with the access gateway 116,the anchor gateway 118, or both.

The Home Subscriber Server (HSS) 130 can be a master user database thatsupports IMS network entities that handle calls. The HSS 130 storessubscription-related information (subscriber profiles), performsauthentication and authorization of the user, and can provideinformation about the subscriber's location and IP information. The HSS130 also maintains binding information on which gateway is currentlyserving a UE. Even when the UE 134 is detached from the network, the HSS130 maintains the binding information until the UE 134 re-attachesitself and updates the binding information. The AAA server 130 canprovide authentication, access control, and accounting to the network.The authentication can involve verification of the subscriber, theaccess control can involve granting or denying access to specificservices, and the accounting that can take place is the tracking of theuse of network resources by subscribers. Other servers, such as the HomeLocation Register (HLR) can be used in other embodiments. In certainembodiments, the AAA/HSS 130 can communicate with the access gateway 116for charging purposes.

The LTE communication network includes a PDN gateway (PGW) 118, aserving gateway (SGW) 116, an E-UTRAN (evolved-UMTS terrestrial radioaccess network) 110, and a mobility management entity (MME) 120. Theevolved packet core (EPC) of an LTE communication network includes theMME 120, SGW 116 and PGW 118 components. In some embodiments, one ormore EPC components can be implemented on the same gateway or chassis asdescribed below.

The SGW sits in the user plane where it forwards and routes packets toand from the eNodeB and PGW. The SGW also serves as the local mobilityanchor for inter-eNodeB handover and mobility between 3GPP networks. TheSGW routes and forwards user data packets, while also acting as themobility anchor for the user plane during inter-eNB handovers and as theanchor for mobility between LTE and other 3GPP technologies (terminatingS4 interface and relaying the traffic between 2G/3G systems and PGW).For idle state UEs, the SGW terminates the down link data path andtriggers paging when down link data arrives for the UE. The SGW managesand stores UE contexts, e.g. parameters of the IP bearer service andnetwork internal routing information. The SGW also performs replicationof the user traffic in case of lawful interception.

The PGW acts as the interface between the LTE network and other packetdata networks, such as the Internet or SIP-based IMS networks (fixed andmobile). The PGW serves as the anchor point for intra-3GPP networkmobility, as well as mobility between 3GPP and non-3GPP networks. ThePGW acts as the Policy and Charging Enforcement Function (PCEF), whichmanages Quality of Service (QoS), online/offline flow-based chargingdata generation, deep-packet inspection, and lawful intercept. The PGWprovides connectivity to the UE to external packet data networks bybeing the point of exit and entry of traffic for the UE. A UE may havesimultaneous connectivity with more than one PGW for accessing multiplepacket data networks. The PGW performs policy enforcement, packetfiltering for each user, charging support, lawful interception, andpacket screening. The PGW also provides an anchor for mobility between3GPP and non-3GPP technologies such as WiMAX and 3GPP2 standards (CDMA1× and EVDO).

The MME resides in the EPC control plane and manages session states,authentication, paging, mobility with 3GPP 2G/3G nodes, roaming, andother bearer management functions. The MME can be a standalone elementor integrated with other EPC elements, including the SGW, PGW, andRelease 8 Serving GPRS Support Node (SGSN). The MME can also beintegrated with 2G/3G elements, such as the SGSN and GGSN. Thisintegration is the key to mobility and session management interworkingbetween 2G/3G and 4G mobile networks.

MME 120 is a control-node for the LTE access network. The MME isresponsible for UE tracking and paging procedures includingretransmissions. MME 120 handles the bearer activation/deactivationprocess and is also responsible for choosing the SGW for a UE at theinitial attach and at time of an intra-LTE handover. The MME alsoauthenticates the user by interacting with the HSS 130. The MME alsogenerates and allocates temporary identities to UEs and terminatesNetwork Access Server (NAS) signaling. The MME checks the authorizationof the UE to camp on the service provider's Public Land Mobile Network(PLMN) and enforces UE roaming restrictions. The MME is the terminationpoint in the network for ciphering/integrity protection for NASsignaling and handles the security key management. Lawful interceptionof signaling is also supported by the MME. The MME provides the controlplane function for mobility between LTE and 2G/3G access networks withthe S3 interface terminating at the MME from the SGSN (not shown). TheMME terminates the S6a interface towards the home HSS for roaming UEs.

The ePDG 122 is responsible for interworking between the EPC and fixednon-3GPP access technologies such as a Wi-Fi, WiMAX, LTE metro, andfemtocell access networks. The ePDG 122 can use IPSec/IKEv2 to providesecure access to the EPC network. Optionally, the ePDG can use ProxyMobile IPv6 (PMIPv6) to interact with the PGW when the mobile subscriberis roaming in an untrusted non-3GPP system. The ePDG is involved intunnel authentication and authorization, transport level packet markingin the uplink, policy enforcement of Quality of Service (QoS) based oninformation received via Authorization, Authentication, Accounting (AAA)infrastructure, lawful interception, and other functions.

FIG. 2 illustrates a communication network that implements afine-grained link adaptation mechanism in accordance with universalmobile telecommunications systems (UMTS) network devices in accordancewith some embodiments. The transceivers include base transceiver station(BTS) 200 and NodeB transceiver 202. The BTS 200 can communicate with aGSM EDGE Radio Access Network (GERAN) 204 and the NodeB 202 cancommunicate with a UMTS terrestrial radio access network (UTRAN) 206.The serving GPRS support node (SGSN) can be implemented on a gateway 208with a mobility management entity (MME). The GERAN 204 can communicatethrough the SGSN functionality on gateway 208 to serving gateway (SGW)212 or gateway GPRS support node (GGSN)/PGW 214.

In some embodiments, the gateways, such as PGW/HA 118, PDSN/HSGW/SGW116, SGSN/MME 208, PGW/GGSN 214, or SGW 212 and/or data centers 132, canaccess and maintain information relating to the communication session,the subscriber, the radio bearers, and the policies relating to thecommunication session. The gateways may be used to provide variousservices to a UE 134 and implement the quality of service (QoS) onpacket flows. Several of these functions are used in providing, forexample, voice over IP (VoIP) routing and enhanced services, such asenhanced charging, stateful firewalls, traffic performance optimization(TPO). The communication networks also allow provision of applicationssuch as VoIP, streaming video, streaming music, multi-user gaming,location-based services, and a variety of delivered to a mobile node.Residing within the gateways can be one or more network processingunits, line cards, as well as packet and voice processing cards.

A base station can be configured to wirelessly communicate with the UE134 according to any of a variety of wireless communication standards.The base station 300 can be configured to employ packet retransmissionscheme such as a HARQ scheme in connection with transmissions sent to UE134.

A base station, which may include an eNodeB transceiver 108, basetransceiver station (BTS) 200, NodeB transceiver 202, Wi-Fi/Femto/smallcell/untrusted/other transceiver 112, can include a plurality ofantennas. The plurality of antennas can provide wireless communicationswith a plurality of UE 134. Each UE 134 can include at least oneantenna, but in general each may include a plurality of antennas.

A base station can be configured to use a link adaptation scheme inorder to control the link reliability and the packet retransmission ratefor reliability and throughput enhancements. For example, the basestation can receive from the UE 134 a message containing SINRinformation, and use the SINR information to compute a fading margin dueto retransmission and an effective SINR. The base station can use theeffective SINR to select a modulation and coding scheme (MCS) fordownlink transmissions to the UE 134.

FIG. 3 illustrates a base station in accordance with some embodiments.The base station 300 can include a processor 302, a memory device 304, atransmitter module 306, a receiver module 308, a controller module 310,and an interface 314.

In some embodiments, the interface 314 can be implemented in hardware tosend and receive signals in a variety of mediums, such as optical,copper, and wireless, and in a number of different protocols some ofwhich may be non-transient. The interface 314 can include a plurality ofantennas that provides communication channels to the transmitter module306 and the receiver module 308 for communication with othercommunication devices, such as UE 134.

In some embodiments, the transmitter module 306 can include individualtransmitter circuits that supply signals to antennas in the interface314 for transmission. For simplicity, these individual transmittercircuits are not shown.

In some embodiments, the receiver module 308 can receive signals fromthe interface 314 and supply the signals to the controller module 310.It is understood that the receiver module 308 may include a plurality ofindividual receiver circuits. For simplicity, these individual receivercircuits are not shown.

The controller module 310 can supply data (in the form of transmitsignals) to the transmitter module 306 and process signals received bythe receiver module 308. In addition, the controller module 310 canperform other transmit and receive control functionality. In someembodiments, the controller module 310 can apply downlink beamformingweight vectors to the multiple downlink transmission streams (e.g.,symbol streams) to produce transmit signals. The controller module 310can supply the transmit signals to the transmitter 306 and thetransmitter module 306 can modulate the respective transmit signals fortransmission via the interface 314.

In some embodiments, the controller module 310 can include a MCS module312. The MCS module 312 can coordinate the link adaptation operation forthe base station 300. In some embodiments, the MCS module 312 can causethe controller module 310 to perform the fine-grained link adaptationmechanism described herein.

In some embodiments, one or more of the modules 306, 308, 310, 312 canbe implemented in software using the memory 304. The software can run ona processor 302 capable of executing computer instructions or computercode. The processor 302 might also be implemented in hardware using anapplication specific integrated circuit (ASIC), programmable logic array(PLA), digital signal processor (DSP), field programmable gate array(FPGA), or any other integrated circuit. The processor 302 suitable forthe execution of a computer program include, by way of example, bothgeneral and special purpose microprocessors, digital signal processors,and any one or more processors of any kind of digital computer.Generally, the processor 302 receives instructions and data from aread-only memory or a random access memory or both.

In some embodiments, one or more of the modules (e.g., modules 306, 308,310, 312) can be implemented in hardware using an ASIC(application-specific integrated circuit), PLA (programmable logicarray), DSP (digital signal processor), FPGA (field programmable gatearray), or other integrated circuit. In some embodiments, two or moremodules 306, 308, 310, 312 can be implemented on the same integratedcircuit, such as ASIC, PLA, DSP, or FPGA, thereby forming a system onchip. Subroutines can refer to portions of the computer program and/orthe processor/special circuitry that implement one or more functions.

The modules 306, 308, 310, 312 can be implemented in digital electroniccircuitry, or in computer hardware, firmware, software, or incombinations of them. The implementation can be as a computer programproduct, e.g., a computer program tangibly embodied in amachine-readable storage device, for execution by, or to control theoperation of, a data processing apparatus, e.g., a programmableprocessor, a computer, and/or multiple computers. A computer program canbe written in any form of computer or programming language, includingsource code, compiled code, interpreted code and/or machine code, andthe computer program can be deployed in any form, including as astand-alone program or as a subroutine, element, or other unit suitablefor use in a computing environment. A computer program can be deployedto be executed on one computer or on multiple computers at one or moresites.

The base station 300 can be operatively coupled to external equipment,for example factory automation or logistics equipment, or to acommunications network, for example a factory automation or logisticsnetwork, in order to receive instructions and/or data from the equipmentor network and/or to transfer instructions and/or data to the equipmentor network. Computer-readable storage devices suitable for embodyingcomputer program instructions and data include all forms of volatile andnon-volatile memory, including by way of example semiconductor memorydevices, e.g., DRAM, SRAM, EPROM, EEPROM, and flash memory devices;magnetic disks, e.g., internal hard disks or removable disks;magneto-optical disks; and optical disks, e.g., CD, DVD, HD-DVD, andBlu-ray disks.

Parts of the functions of the transmitter module 306, receiver module308, and controller module 310 may be implemented in a modem and otherparts of the transmitter module 306 and receiver module 308 may beimplemented in radio transmitter and radio transceiver circuits. Itshould be understood that there are analog-to-digital converters (ADCs)and digital-to-analog converters (DACs) in the various signal paths toconvert between analog and digital signals.

While the controller module 310 is depicted as a part of the basestation 300, the controller module 310 can be a separate entity or apart of a separate entity from the base station 300. For example, thecontroller module 310 can reside in a serving gateway in communicationwith the base station 300 to provide fine-grained link adaptation. Asanother example, the controller module 310 can reside in an anchorgateway in communication with the base station 300 to providefine-grained link adaptation.

In some embodiments, the controller module 310 can implement Inter-cellInterference Coordination (ICIC). ICIC is a method used in a LTE networkto manage interference of signals generated by adjacent cells. ICICcoordinates the transmission of signals in adjacent cells so that theadjacent cells do not use the same frequency-time resources. ICICcoordinates the signal transmissions between cells by providing acommunication mechanism between base stations over an X2 interface.

For downlink ICIC, the controller module 310 can reduce signalinterference by controlling the downlink transmission power of RBs. Forexample, when a first base station is using a particular RB with hightransmission power, the controller module 310 in the first base stationcan notify a second base station that the particular RB is used withhigh transmission power. In response to receiving the notification, thesecond base station can schedule its signal transmission so that thesecond base station does not use high transmission power with theparticular RB. In some embodiments, the controller module 310 can sharesuch resource block scheduling information using a Relative NarrowbandTransmit Power (RNTP) message.

However, because the ICIC mechanism may not entirely remove signalinterference between adjacent cells, it is desirable to perform linkadaptation that accounts for the signal interference between adjacentcells. In some sense, the CQI based link adaptation mechanism does takeinto account the signal interference between adjacent cells. The CQIprovided by UE 134 can capture average interference within a sub-band offrequencies (in case of a sub-band CQI) or the cell's entire bandwidth(in case of a wide-band CQI). Therefore, by selecting the MCS based onthe CQI, the base station 300 can take into account the interferencebetween cells.

However, the CQI-based link adaptation mechanism may not accuratelyaccount for the interference between cells. Oftentimes, base stations indifferent cells can control the downlink transmit power at a RBgranularity. Therefore, the interference level can be different from oneRB to another. However, the CQI cannot provide the fine-grainedinterference information at the RB granularity because the CQI merelyprovides an interference level averaged over a broader set of frequencybands. Therefore, the CQI-based link adaptation mechanism may notaccurately account for the interference between cells.

In some embodiments, the MCS module 312 in the controller module 310 canprovide a fine-grained link adaptation mechanism that is capable ofadapting to the interference level at a RB granularity. To this end, theMCS module 312 can compute the effective SINR for particular UE and forindividual RBs. The effective SINR for individual RBs can be computed byexplicitly accounting for the difference in SINR for individual RBs.

FIG. 4 illustrates a process for determining an effective SINR for aparticular RB in accordance with some embodiments. In step 402, the MCSmodule 312 is configured to determine a CQI SINR γ_(CQI)(i,j,k) based onthe CQI reported by UE 134 for a sub-band that includes the particularRB. The index i refers to UE; the index j refers to a cell, and theindex k refers to the particular RB.

In some embodiments, the CQI SINR γ_(CQI) can be computed as follows:

${\gamma_{CQI}\left( {i,j,k} \right)} = \frac{{P_{CRS}(j)}{E\left\lbrack {G\left( {i,j,k} \right)} \right\rbrack}}{E_{INT}}$where P_(CRS)(j) is the Cell Specific Reference Signal (CRS) Energy PerResource Element (EPRE) for the cell j; E[ ] is an expectation operator;E_(INT) is the average interference; and G(i,j,k) is the channel gainfrom the cell j to UE i on RB k. In some embodiments, the MCS module 312can compute the CQI SINR γ_(CQI)(i,j,k) using a standard techniqueemployed in the industry. For example, the MCS module 312 can analyzethe PDSCH transmission scheme and compute bit error curves for the MCSreported in CQI as function of SINR. Then the SINR can be picked ascorresponding to, for example, 99% success for the MCS reported.

In step 404, the MCS module 312 is configured to determine theadaptation factor Δ_(adapt)(i,j,t_(harq)). The adaptation factor can bea SINR margin computed based on the predetermined limit on the number ofpacket retransmissions and/or the MCS previously assigned to the UE i.The MCS module 312 can determine the adaptation factorΔ_(adapt)(i,j,t_(harq)) based on a feedback loop that adjusts theadaptation factor until the selected MCS is successful within thepredetermined number of HARQ retransmissions with a predeterminedprobability. The adaptation factor Δ_(adapt)(i,j,t_(harq)) can capturethe unpredictability of communication channels (e.g., UE mobility) andthe UE specific implementation.

In step 406, the MCS module 312 can determine the interferenceadjustment factor Δ_(ICIC)(i,j,k). The interference adjustment factorΔ_(ICIC)(i,j,k) can be computed as follows:Δ_(ICIC)(i,j,k)=γ_(CQI)(i,j,k)−γ_(PDSCH)(i,j,k)where γ_(CQI) is the SINR computed from the CQI, as discussed above, andγ_(PDSCH) is the SINR on the PDSCH.

In some embodiments, if the sub-band CQI is used, the expectationoperation E[ ] is performed over the sub-band of frequencies associatedwith the CQI; if the wide-band CQI is used, the expectation operation E[] is performed over the entire cell bandwidth. Similarly, in someembodiments, if the sub-band CQI is used, the average interferenceE_(INT) is an average interference over the sub-band of frequenciesassociated with the CQI; if the wide-band CQI is used, the averageinterference E_(INT) is an average interference over the entire cellbandwidth.

In some embodiments, the MCS module 312 can determine the channel gainG(i,j,k) based on the Reference Signal Received Power (RSRP) reported byUE i. For example, the MCS module 312 can receive the RSRP report fromUE i from the cell j. The MCS module 312 can use the RSRP report todetermine P_(CRS)(j)G(i,j,k) assuming flat fading. For example, the MCSmodule 312 can determine P_(CRS)(j)G(i,j,k) based on the RSRP report inaccordance with 3GPP Technical Specification 36.214, entitled “EvolvedUniversal Terrestrial Radio Access (E-UTRA); Physical layer;Measurements,” which is herein incorporated by reference in itsentirety.

Subsequently, the MCS module 312 can determine the CRS EPRE P_(CRS)(j)for the cell j by decoding the System Information Block Type 2 (SIB2)message for the cell j. Therefore, the MCS module 312 can factor out theCRS EPRE P_(CRS)(j) from P_(CRS)(j)G(i,j,k) to determine the channelgain G(i,j,k) for the cell j. In some cases, the channel gain G(i,j,k)may need to be scaled appropriately if the base station 300 uses amultiple-input-multiple-output (MIMO) transceiver.

In some embodiments, the MCS module 312 can estimate the channel gainG(i,j,k) based on a Reference Signal Received Quality (RSRQ) measurementcombined with P_(CRS)(j) (known from the SIB2 message.) The RSRQ isdefined as follows:

${RSRQ} = \frac{N \times {RSRP}}{RSSI}$where N is number of RBs over which RSRQ is measured and RSSI refers toreceived signal strength indication. Therefore, the MCS module 312 canuse the above relationship to derive RSRP from RSRQ, and use the derivedRSRP to determine P_(CRS)(j)G(i,j,k) in accordance with 3GPP TechnicalSpecification 36.214. Thus, based on P_(CRS)(j) known from the SIB2message, the MCS module 312 can estimate the channel gain G(i,j,k).

In some embodiments, the PDSCH SINR γ_(PDSCH) can be determined asfollows:

$\gamma_{PDSCH} = \frac{{P_{PDSCH}\left( {j,k} \right)}{G\left( {i,j,k} \right)}}{\sum\limits_{j^{\prime} \neq j}{{P_{PDSCH}\left( {j^{\prime},k} \right)}{G\left( {i,j^{\prime},k} \right)}}}$where P_(PDSCH)(j,k) is the PDSCH EPRE for the cell j for the particularRB k. It is notable that the EPRE value does not vary with systembandwidth or number of RBs and that the CRS EPRE P_(CRS)(j) is constantacross frequencies, whereas the PDSCH EPRE P_(PDSCH)(j,k) is a functionof the RB index k.

To determine the PDSCH SINR γ_(PDSCH), the MCS module 312 can determineP_(PDSCH)(j,k)G(i,j,k) based on the Reference Signal Received Power(RSRP) reported by UE i. For example, the MCS module 312 can receive theRSRP report from UE i from the cell j. The MCS module 312 can use theRSRP report to determine P_(CRS)(j)G(i,j,k) assuming flat fading.

Given this relationship, the MCS module 312 can transform the formulafor the PDSCH SINR γ_(PDSCH) as follows:

$\gamma_{PDSCH} = \frac{\left( \frac{P_{PDSCH}\left( {j,k} \right)}{P_{CRS}(j)} \right){P_{CRS}(j)}{G\left( {i,j,k} \right)}}{\sum\limits_{j^{\prime} \neq j}{\left( \frac{P_{PDSCH}\left( {j^{\prime},k} \right)}{P_{CRS}\left( j^{\prime} \right)} \right){P_{CRS}\left( j^{\prime} \right)}{G\left( {i,j^{\prime},k} \right)}}}$Since P_(CRS)(j)G(i,j,k) and P_(CRS)(j′)G(i,j′,k) can be determinedusing the RSRP report from the cells j and j′, respectively, the MCSmodule 312 can compute the PDSCH SINR γ_(PDSCH) if the MCS module 312can compute the EPRE ratio

$\left( \frac{P_{PDSCH}\left( {j,k} \right)}{P_{CRS}(j)} \right)$for each cell j and for each RB k.

When the MCS module 312 is in a base station residing in the cell j,then the MCS module 312 can access to the CRS EPRE P_(CRS)(j) and thePDSCH EPRE P_(PDSCH)(j,k) for the cell j. Therefore, the MCS module 312can easily compute the EPRE ratio

$\left( \frac{P_{PDSCH}\left( {j,k} \right)}{P_{CRS}(j)} \right)$for its cell j.

In order to compute the EPRE ratio

$\left( \frac{P_{PDSCH}\left( {j,k} \right)}{P_{CRS}(j)} \right)$for neighboring cells, the MCS module 312 can use one of severalmechanisms. In some embodiments, the MCS module 312 can determine theCRS EPRE P_(CRS)(j) for neighboring cells by decoding SIB2 messages forthe neighboring cells. The MCS module 312 can access the SIB2 messagesfor the neighboring cells using the network listen mode. Also, the MCSmodule 312 can determine the PDSCH EPRE P_(PDSCH)(j,k) for neighboringcells by receiving the total transmission power of neighboring cellsfrom a centralized server in a centralized self-organizing network,and/or an operations, administration and management server (OAM).Subsequently, the MCS module 312 can computationally determine the EPREratio

$\left( \frac{P_{PDSCH}\left( {j,k} \right)}{P_{CRS}(j)} \right)$for neighboring cells based on the CRS EPRE P_(CRS)(j) and the PDSCHEPRE P_(PDSCH)(j,k) for neighboring cells.

In some embodiments, the MCS module 312 can determine the EPRE ratio

$\left( \frac{P_{PDSCH}\left( {j,k} \right)}{P_{CRS}(j)} \right)$for neighboring cells based on an RNTP message. The RNTP message canindicate, for each cell and for each RB, whether the PDSCH EPRE isgreater than a predetermined threshold. If the PDSCH EPRE for aparticular RB is greater than the predetermined threshold, the RB can belabeled as “1”; if the PDSCH EPRE for a particular RB is not greaterthan the predetermined threshold, the RB can be labeled as “0.”

In some cases, to compute the EPRE ratio, the MCS module 312 can beconfigured to receive the power transmission levels (e.g., powerspectral density level) for RBs marked 0 and 1 in the RNTP message. Forexample, the MCS module 312 can be configured to receive the powertransmission levels P_(PDSCH)(j,k) for RBs marked 0 and 1 from acentralized server and/or an OAM. In some embodiments, the MCS module312 can be configured to translate the power transmission levelsP_(PDSCH)(j,k) into the EPRE ratio assuming that the CRS EPRE is equalto the total power distributed equally across all CREs. In otherembodiments, the MCS module 312 can be configured to translate the powertransmission levels P_(PDSCH)(j,k) into the EPRE ratio based on anexplicit knowledge of the CRS EPRE P_(CRS)(j).

In step 408, the MCS module 312 can determine the effective SINR foreach RB based on the CQI SINR γ_(CQI)(i,j,k), the adaptation factorΔ_(adapt)(i,j,t_(harq)), and the interference adjustment factorΔ_(ICIC)(i,j,k) as follows:γ_(EFF)(i,j,k)=γ_(CQI)(i,j,k)+Δ_(adapt)(i,j,t _(harq))+Δ_(ICIC)(i,j,k)Subsequently, the MCS module 312 can use the effective SINR to determinethe MCS for link adaptation.User Equipment

The UE 134 described above can communicate with a plurality of radioaccess networks using a plurality of access technologies and with wiredcommunication networks. The UE 134 can be a smart phone offeringadvanced capabilities such as word processing, web browsing, gaming,e-book capabilities, an operating system, and a full keyboard. The UE134 may run an operating system such as Symbian OS, iPhone OS, RIM'sBlackberry, Windows Mobile, Linux, Palm WebOS, and Android. The screenmay be a touch screen that can be used to input data to the UE 134 andthe screen can be used instead of the full keyboard. The UE 134 may havethe capability to run applications or communicate with applications thatare provided by servers in the communication network. The UE 134 canreceive updates and other information from these applications on thenetwork.

The UE 134 also encompasses many other devices such as televisions(TVs), video projectors, set-top boxes or set-top units, digital videorecorders (DVR), computers, netbooks, laptops, and any otheraudio/visual equipment that can communicate with a network. The UE 134can also keep global positioning coordinates, profile information, orother location information in its stack or memory. The UE 134 can have amemory such as a computer readable medium, flash memory, a magnetic diskdrive, an optical drive, a programmable read-only memory (PROM), and/ora read-only memory (ROM). The UE 134 can be configured with one or moreprocessors that process instructions and run software that may be storedin memory. The processor can also communicate with the memory andinterfaces to communicate with other devices. The processor can be anyapplicable processor such as a system-on-a-chip that combines a CPU, anapplication processor, and flash memory. The interfaces can beimplemented in hardware or software. The interfaces can be used toreceive both data and control information from the network as well aslocal sources, such as a remote control to a television. The UE 134 canalso provide a variety of user interfaces such as a keyboard, a touchscreen, a trackball, a touch pad, and/or a mouse. The UE 134 may alsoinclude speakers and a display device in some embodiments.

In some embodiments, the software needed for implementing a process or adatabase includes a high level procedural or an object-orientatedlanguage such as C, C++, C#, Java, or Perl. The software may also beimplemented in assembly language if desired. Packet processingimplemented in a network device can include any processing determined bythe context. For example, packet processing may involve high-level datalink control (HDLC) framing, header compression, and/or encryption. Incertain embodiments, the software is stored on a storage medium ordevice such as read-only memory (ROM), programmable-read-only memory(PROM), electrically erasable programmable-read-only memory (EEPROM),flash memory, or a magnetic disk that is readable by a general orspecial purpose-processing unit to perform the processes described inthis document. The processors can include any microprocessor (single ormultiple core), system on chip (SoC), microcontroller, digital signalprocessor (DSP), graphics processing unit (GPU), or any other integratedcircuit capable of processing instructions such as an x86microprocessor.

Although the present disclosure has been described and illustrated inthe foregoing example embodiments, it is understood that the presentdisclosure has been made only by way of example, and that numerouschanges in the details of implementation of the disclosure may be madewithout departing from the spirit and scope of the disclosure, which islimited only by the claims which follow. Other embodiments are withinthe following claims. For example, the popularity tracking module can beplaced in a gateway.

The invention claimed is:
 1. A method for communicating with a receiverusing a modulation and coding scheme (MCS), the method comprising:determining, at a transmitter in communication with the receiver in acommunications network, an interference adjustment factor that accountsfor a signal interference level for a particular resource block, whereindetermining the interference adjustment factor includes determining adifference between (1) a signal-to-interference-plus-noise ratio (SINR)derived from channel state information corresponding to the particularresource block and (2) a SINR of a downlink data channel for theparticular resource block; determining the MCS for the receiver for theparticular resource block based, at least in part, on the interferenceadjustment factor; and communicating with the receiver using thedetermined MCS.
 2. The method of claim 1, wherein determining theinterference adjustment factor includes determining a difference between(1) a signal-to-interference-plus-noise ratio (SINR) derived from thechannel state information corresponding to the particular resource blockand (2) a SINR of a downlink data channel for the particular resourceblock.
 3. The method of claim 1, further comprising determining the SINRof the downlink data channel based on resource block schedulinginformation from neighboring cells.
 4. The method of claim 3, furthercomprising receiving the resource block scheduling information fromtransmitters in the neighboring cells as a part of a Relative NarrowbandTransmit Power (RNTP) message.
 5. The method of claim 1, furthercomprising determining the SINR of the downlink data channel based ondownlink transmission power information associated with neighboringcells received from a centralized server in a centralizedself-organizing network.
 6. The method of claim 1, further comprisingdetermining the SINR of the downlink data channel based on downlinktransmission power information associated with neighboring cellsreceived from an operations, administration and management server (OAM).7. The method of claim 1, further comprising determining the SINR of thedownlink data channel based on a System Information Block Type 2 (SIB2)message associated with neighboring cells.
 8. The method of claim 1,further comprising: deriving an effective SINR for the particularresource block for the receiver based on (1) a first SINR based onchannel state information received from the receiver, (2) an adaptationfactor based on a predetermined limit of a number of packetretransmissions to the receiver, and (3) the interference adjustmentfactor; and determining the MCS for the receiver for the particularresource block based on the effective SINR.
 9. The method of claim 8,wherein determining the adaptation factor includes adjusting theadaptation factor until the determined MCS is successful within thepredetermined limit of packet retransmissions with a predeterminedprobability.
 10. A network device comprising: one or more interfacesconfigured to provide wireless communication with a receiver; and aprocessor, in communication with the one or more interfaces, andconfigured to run a module stored in memory, wherein the network deviceis configured to: determine an interference adjustment factor thataccounts for a signal interference level unique for a particularresource block; wherein determining the interference adjustment factorincludes determining a difference between (1) asignal-to-interference-plus-noise ratio (SINR) derived from channelstate information corresponding to the particular resource block and (2)a SINR of a downlink data channel for the particular resource block;determine a modulation and coding scheme (MCS) for the receiver for theparticular resource block based, at least in part, on the interferenceadjustment factor; and communicate with the receiver using thedetermined MCS.
 11. The network device of claim 10, wherein the moduleis configured to determine a difference between (1) a SINR derived fromthe channel state information corresponding to the particular resourceblock and (2) a SINR of a downlink data channel for the particularresource block.
 12. The network device of claim 10, wherein the moduleis configured to determine the SINR of the downlink data channel basedon resource block scheduling information received from neighboring cellsas a part of a Relative Narrowband Transmit Power (RNTP) message. 13.The network device of claim 10, wherein the module is configured to:derive an effective SINR for the particular resource block for thereceiver based on (1) a first SINR based on channel state informationreceived from the receiver, (2) an adaptation factor based on apredetermined limit of a number of packet retransmissions to thereceiver, and (3) the interference adjustment factor; and determine theMCS for the receiver for the particular resource block based on theeffective SINR.
 14. The network device of claim 10, wherein the moduleis configured to determine the SINR of the downlink data channel basedon downlink transmission power information associated with neighboringcells received from a centralized server in a centralizedself-organizing network.
 15. The network device of claim 10, wherein themodule is configured to determine the SINR of the downlink data channelbased on a System Information Block Type 2 (SIB2) message associatedwith neighboring cells.
 16. A method for determining a modulation andcoding scheme (MCS) for a receiver, the method comprising: determining,at a transmitter in communication with the receiver, asignal-to-interference-plus-noise ratio (SINR) based on channel stateinformation received from the receiver; determining an adaptation factorbased on a predetermined limit of a number of packet retransmissions tothe receiver; determining an interference adjustment factor thataccounts for a signal interference level at a resource blockgranularity; determining the MCS for the receiver at the resource blockgranularity based, at least in part, on the SINR, the adaptation factor,and the interference adjustment factor; and communicating with thereceiver using the determined MCS.
 17. The method of claim 16, whereindetermining the interference adjustment factor includes determining adifference between (1) a SINR derived from the channel state informationat the resource block granularity and (2) a SINR of a downlink datachannel at the resource block granularity.
 18. The method of claim 17,further comprising determining the SINR of the downlink data channelbased on resource block scheduling information from neighboring cells.19. The method of claim 18, further comprising receiving the resourceblock scheduling information from transmitters in the neighboring cellsas a part of a Relative Narrowband Transmit Power (RNTP) message. 20.The method of claim 17, further comprising determine the SINR of thedownlink data channel based on a System Information Block Type 2 (SIB2)message associated with neighboring cells.